US2580496A - Separation of rosin acids - Google Patents

Description

Patented Jan. 1, 1952 ts -to- ,The Fulwa lChemical Corpo- Wale ironing." (Giesemann) n n LT1.

` `This `inventionQ relates to ,separationwof .i aidsandistconcerned withxwosphases o s uch Separation., one, phase providgffn Sparationef mixed rosin `acids frorfifosinY materia-1s containng .other constituents, and thefotherphase Fprof The solution thus prepared'cntins the `rlii'sin "acd "-s aitseas lsoluteebut with#l the neutrals inf-an undissolyed state. The solution is then-extracted 'with ethrfandj-aftr separation ofL the etherflayy stitgent father' than ifaetgydroabienc aciers still 'pre'sntfieven"afterithe selective separation l ofA `the hydrabi'tic aCidS'; but that the dehydroabie'tic 3 acid may even be separated from such minor fraction.

With the foregoing general description of the process in mind, attention is now directed to certain variables and examples.

First note that the alkali to be employed fin preparing the aqueous solution may be any of the alkali metal hydroxides and carbonates such as sodium hydroxide or sodium carbonate. As already indicated, the quantity of alkali present during the first phase of treatment, i. e., the phase for separation of neutrals, should be only sufficient to react with the rosinracids present. This, of course, will depend upon the particular rosin material being treated.

The presence of excess alkali at the time of the second phase of the treatment, i. e., the fractional acidification, is of no detriment, but would,`

of course, require the addition of moreacid in order to reduce the pH rvalue of the solution to the range in which the rosin acids may be precipitated.

For the purpose of extracting the neutrals after initial preparation of the solution of the sodium salts of the rosin acids, a non-polarv solvent should be employed, such as ether.

The concentration of the rosin acid Vsalts in the aqueous solution is not critical. It is Vpreferred, however, to employ a dilute solution because this enables greater precision in the separation of rosin acids, for instance a concentration of from a fraction of 1% up to 10% based on, the rosin acids. A concentration of from 3% tov 5% has been found to be particularly eiective.v

A mineral acid should be usedfor the fractional acidication of the solution, for instance hydrochloric acid or sulfuric acid, hydrochloric acid being preferred. It is further preferred to yuse the acid in dilute form, say from 0.1 to 0.5 normal, advantageously 0.1 normal. Y l

The amount of acid added at each stage ofthe frictional acidification will, of course, depend upon the fractions desired to be separated and this in turn will depend upon the proportions of the various rosin acids present in the mixture taken for treatment.

Efficient or thorough stirring should be used during the acid addition, sinceA the precision of separation Yof the desired rosin acid fractions is thereby greatly enhanced. I

All operations are effective -at room temperature. There is no advantage at all in working at.' other temperatures in the rst phase of treatment. However, the second phase may well be carried out at higher temperatures, even at the boiling point, during the addition of mineral acid andin this case each addition of mineral acid should be followed by cooling to room temperature before filtration. In this way the sharpness of the separation is enhanced by the additional factor of crystallization.

It is here further pointed out that the rst phase of the treatment (separation of neutrals) may be applied not only to various disproportionated rosins, but even to other rosin materials where a separation of neutrals is desired.

In use of the invention for securing dehydroabietic acid in relatively pure form, any of a variety of disproportionated rosins may be selected as starting material. Thus, the type of product resulting from palladium-charcoal disproportionation may be used, or, if desired, dehydroabietic acid may be separated from rosin which has been disproportionated by heating in the presence of sulfur dioxide, as disclosed, for

4 example, in Nicholas L. Kalman Patent No. 2,378,295.

EXAMPLES Example 1.-This example illustrates the separation of neutrals from a disproportionated rosin.

Rosin disproportionated with palladium-charcoal was used in this example. The disproportionated material contained about 55% dehydroabietic acid, about 33% hydroabietic acids, and 12% neutrals. 34.1 g. of this disproportionated rosin (containing g. of rosin acids, 0.1 mol, and 4.1 g. neutrals) was ground in a mortar and then dissolvedv in 500 ml. of water and 205 ml. of 0.489 N, sodium hydroxide (0.1 mol sodium hydroxide) heated to 95 C. The solution was agi- .tated and allowed to cool, thus yielding a turbid .solution containing 3% rosin acids in the form of their `sodium salts. This solution was then shaken with 800 ml. of ether and allowed to stand. The clear, almost colorless, aqueous layer was removed and the ether layer evaporated to dryness, yielding 4.6 g. of light brown, viscous oil. The aqueous solution was then shaken with V 500 ml. of ether and separated. This time the ether extract gave 0.5 g. of a light yellow sticky solid. Vacuum and warming removed the ether dissolved in the aqueous solution, and complete acidification of a portion of this aqueous solution gave a white precipitate of mixed rosin acids, having acid number 181.

Additional batches of g. and 175 g. of the same disproportionated rosin were worked up with the same results.

Example 2.--Neutrals were separated from another disproportionated rosin, as follows:

In this example a disproportionated rosin was prepared with the use of sulfur dioxide. 179.8 g. of this rosin (150 g. rosin acids, 0.5 mol and 29.8 g. neutrals) was dissolved in the same manner described in Example 1 above in a solu.- tion containing 0.5 mol of sodium hydroxide and sufficientv water to make 5 liters yielding a solution containing 3% of rosin acids in the form of theirV sodium salts. This was decanted from 1.9 g. of an insoluble, viscous oil found to be present. One liter of the decanted solution was shaken with 800 ml. of ether and separated. The ether layer contained 4.7 g. of an oily material. This portion of the aqueous solution was again extracted with ether. yielding an addi'- tional 0.7 g. of oil. On complete acidiiication of a portion of the extracted solution a tine white precipitate was obtained having an acid number of 170.

Example 3,-The following illustrates the fractional acidification of rosin disproportionated with palladium-charcoal and previously freed from neutrals in accordance with Example l above.

An aqueous solution having a total volume of 2500 m1. and containing 58.75 g. of the mixed rosin acids as their sodium salts (2.35% with respect to the acids) was subjected to fractional acidification, being eilciently stirred throughout. The initial pH of the solution was 10.85 and this was lowered. by vgradual addition of 0.103 N hydrochloric acid.v The rate of addition varied between 0.5 and 2.5 ml. per minute, depending upon the amount of precipitation produced. A fter each minute of addition the flow of acid was stopped and the pH recorded following the lapse of another minute. acidication in which the first fraction was precipitated the pH of the solution decreased During the yai:enlace to 9 and remained at this value through- 'oiit the precipitation of the first fraction. After iiitration of this first fraction, the filtrate was acidied-further, during which theypH sank to 8.65 'with no precipitation. Further acid addition precipitated" another' fraction :between pH additional `fractions were manner 'a number of `folztfained, `and the `finalfraction wasv precipitated by "the *addition 'of excess acid to remove come p letely all remaining rosi'n acid nthe solution. The precipitates after filtration, were washed "free :f `chloride ion with 'water,` dried and WEIC. n 4

The quantity of precipitate securedin each of seven fractions according to the foregoing, and other pertinent data' are given in Table I just below.

For identification purposes exactly equal amounts of each of the seven fractions, and also of an authentic sample of pure dehydroabietic acid, were esterifed with excess dioazomethane in ether and any crystalline methyl dehydroabietate carefully isolated for yield and purity. The results of these esterifications are given in Table II just below.

From the above it will be seen that fraction 5 is substantially pure dehydroabietic acid and that fractions 4 and 6 are mainly composed of this acid. A correction Value of 4% may be added to the actual percentages of ester obtained for these three fractions, since the yield percentage of ester from pure dehydroabietic acid indicates 4% loss by ester solubility in the crystallizing solvent, methyl alcohol. It will be seen therefore that, based on the amount of methyl ester isolated from the three esteried. fractions, 5060% of the theoretical amount of dehydroabietic acid in the mixed acids has been separated in a state of purity suii'cient for virtually any purpose.

Example 4.-'I`his example illustrates fractional acidification of mixed rosin acids by the use of hydrochloric acid and sodium carbonate.

The mixed acids taken for treatment comprised about 63% dehydroabietic acid andt37% hydroabietic acids. A batch of 30 g. of the mixed acids g. of sodium carbonate.

was dissolved in 30001111. of water "containing 10.7 rIhis formed a clear solution at room temperature and had aninitial pH of 9.3. Y

The solution was brought to a boil and 0.1 N hydrochloric acid was added dropwisc with stirrring tbthe point :of incipient turbidityywhere- 'upon the solution was cooled to room temperature, resulting in precipitation and crystallization of a small fraction which was ltered, washed with water, and crystallized once from `aqueous ethanol. v i The filtrate was again raised to boiling `temperature and hydrochloric acid again added in the manner described `above to secure another small fraction. This 'fractionating treatment was `repeated until no more precipitate wa's secured,

and thereby 25 fractions were obtained.

The pH of th-e solution being fractionated was Itaken after each filtration, and it was Vfound that the"`f1'"act`ions precipitated between a pH of 'about 8.5 Ia'ndlabout '1.5 (fractions 16 to'2l of the series) comprised substantially puredehydroabietic acid. This was shown by combining this group of frac- 'tions and establishing the neutralization equivalent thereof, which was 298. Calculated for pure dehydroabietic acidi: 298. Y Y

' A sample of the above combined fractions was 'esteri'iied with dimethyl sulfate in the usual manner, from which pure methyl dehydroabietata `of melting peint ST1-652 C., was obtained'.` Amixed melting point with authentic methyl dehydroabietate showed no depression.

It will be understood that where it is desired to separate dehydroabietic acid, Without separation of other individuals with respect to each other, the fractional acidication may be carried out merely in two stages, instead of a multiplicity. When operating in this Way, the quantity of acid added in the first stage of acidication should be sufficient to bring the pH value of the solution down to about 8.5. This will effect precipitation of the bulk of the acids present other than dehydroabietic acid. A second addition of acid may then be made to the solution suiicient to bring the pH down to about 7.5. This second stage of acidification will yield a precipitate constituting substantially pure dehydroabietic acid, the quantity of which will be over one-half of the total quantity of dehydroabietic acid initially present in the mixed acids taken for treatment.

Such two-stage fractional acidification has been effected under the general conditions fully outlined above, with results as to yield and purity of the same order as those indicated by the tables given above.

I claim: t

1. The method of separating dehydroabietic acid from disproportionated rosin comprising dissolving disproportionated rosin in an aqueous alkaline solution to thereby form an aqueous solution of the alkali salts of the rosin acids present, adding mineral acid to the solution in an amount suiiicient to react with the alkali salts of the hydroabietic acids present but insufficient to react with the alkali salts of dehydroabietic acid present, separating the resulting precipitate `of hydroabietic acids, and thereafter recovering the dehydroabietic acid constituent from the solution.

2. A method according to claim 1 in which the addition of mineral acid is effected in two stages, the rst of which is sulcient to reducethe pH value of the solution to 8.50 to thereby precipitate rosin acids other than dehydroabietic acid,

and the second of which is sufficient to reduce the pH value of the remaining solution to 7.50 to thereby precipitate dehydroabietic acid.

3. The method of separating dehydroabietic -acid from disproportionated rosin comprising separating neutral constituents from such rosin,

reacting- `the rosin acids present with an alkali selected from the class consisting of alkali hydroxiclesand alkali carbonates in aqueous solution to `thereby form an aqueous solution of thel alkali salts of said acids, adding mineral acid to the solution in an amount suiiicient to react with the alkali salts of the hydroabietic acids present but insufficient to react with the alkali salts of dehydroabietic acid present, separating the resulting precipitate of hydroabietic acids., and

thereafter recovering the dehydroabietic acid constitutent from the solution.

4. A method according to claim 3 in which the disproportionated rosin is first dissolved in an i8 rosin acids from rosln materialsvcontaining such acids in admixture with neutral constitutents, which method comprises dissolving said rosin material in an aqueous alkaline solution containing a quantity of an alkali selected from the group consisting of alkali hydroxides and alkali carbonatessubstantially equal to but not greater than that quantity required to react with the rosin acids present to thereby form an aqueous solution of the alkali salts of the rosin acids having the neutral constituents suspended therein, extracting the solution with ether, and thereafter recovering the rosinacid constituents. A

7. A method according to claim 6 in which the recovery of the rosinvacid constitutents is effected by .fractional acidification of the solution after .extraction of the neutrals.

HAROLD H. zExss i REFERENCES CITED v The following references are of record in the tile of this patent:

UNITED STATES PATENTS 2631-2636, November 1938.

Claims (1)

1. THE METHOD OF SEPARATING DEHYDROABIETIC ACID FROM DISPROPORTIONATED ROSIN COMPRISING DISSOLVING DISPROPORTIONED ROSIN IN AN AQUEOUS ALKALINE SOLUTION TO THEREBY FORM AN AQUEOUS SOLUTION OF THE ALKALI SALTS OF THE ROSIN ACIDS PRESENT, ADDING MINERAL ACID TO THE SOLUTION IN AN AMOUNT SUFFICIENT TO REACT WITH THE ALKALI SALTS OF THE HYDROABIETIC ACIDS PRESENT BUT INSUFFICIENT TO REACT WITH THE ALKALI SALTS OF DEHYDROABIETIC ACID PRESENT, SEPARATING THE RESULTING PRECIPITATE OF HYDROABIETIC ACIDS, AND THEREAFTER RECOVERING THE DEHYDROABIETIC ACID CONSTITUENT FROM THE SOLUTION.